As is known, losses in the form of heat occur in electric machines, such as generators, during the conversion of mechanical energy into electrical energy, and vice versa. It is therefore necessary to cool active components, i.e. those in which losses occur, as efficiently as possible. A maximum permissible limit value temperature is given from the insulating material classes, which electrically insulate current-conveying components from one another and with respect to the housing. During operation it must be ensured that these limit value temperatures are not exceeded, since otherwise the necessary insulation is no longer provided.
In addition, due to the resultant heating of the electric machine, the maximum performance at which the electric machine can be operated is limited. There is thus an interest in cooling the electric machine as efficiently as possible.
Cooling circuits that dissipate heat from the interior of the generator by means of a thermodynamic cycle and typically deliver said heat to a second medium via a heat exchanger are mostly used when it comes to cooling in electric machines.
Due to a suitable selection of the geometry within the electric machine, a flow network is produced within the electric machine, by means of which network the components to be cooled are supplied with coolant. The geometry of the flow network defines a ratio of coolant mass flows in which the individual active component parts, for example rotor, stator, laminated core end zones, the stator winding region and/or laminated core and tabs at the stator winding head, are cooled. For a given electric machine, the geometry of the flow network and therefore the ratio of the coolant mass flows to one another are defined, which results in a likewise defined cooling ratio. For electric machines in the prior art, it is typically not possible to actively influence this ratio of the cooling mass flows to one another. In particular, it is thus impossible to adapt the cooling to different operating states of the electric machine.